EA011146B1 - Method for direct and continuous production of hollow bodies from a polyester melt - Google Patents

Abstract

The invention relates to a method and a device for producing moulded bodies from a highly condensed polyester melt. The invention is characterised in that the melt never solidifies between the polycondensation reactor and the moulding units and that there is no degassing device between the end reactor and said moulding units.

Description

The present invention relates to a continuous method for the direct manufacture of molded articles from highly condensed polyester melt.

Below, instead of the term "molded products", the term "hollow bodies" is used. The present invention, with appropriate modifications, is applicable to the manufacture of not only hollow bodies, but also sheets and films that meet the requirements comparable to those for hollow bodies.

Known aromatic polyesters or copolyesters, particularly polyethylene terephthalate and copolymers thereof with a minor content of, for example, isophthalic acid or cyclohexanedimethanol, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate and copolyesters, used as starting materials for making hollow bodies, after their preparation, carried out by polycondensation of in the melt, at a certain characteristic viscosity, which, for example, for polyethylene terephthalate and corresponding nizkomodifitsirovannyh their copolyesters is in the range from 0.65 to 0.90 dl / g, are processed to injection molding machines in the hollow body.

Currently used standard technology for the production of polyethylene terephthalate, intended for the manufacture of food packaging, especially bottles, is as follows.

Terephthalic acid, respectively, its esters, is subjected to esterification, respectively, transesterification with ethylene glycol at the stage of esterification, which can be implemented in one or more series-connected reactors.

The resulting esters with a subsequent increase in temperature and a decrease in pressure are subjected to melt polycondensation before the formation of polyethylene terephthalate with an average characteristic viscosity of from 0.55 to 0.65 dl / g, which is cooled and granulated. Polycondensation is usually carried out in at least two stages: first, in the so-called pre-condensation reactor, and then in the final reactor, which is also generally referred to below as condensation reactors. Depending on the production capacity of the equipment and other circumstances, it is also possible to use a larger number of sequentially connected condensing reactors.

The melt leaving the final reactor is granulated and the obtained granulated polyethylene terephthalate is sent to a solid phase polycondensation reactor carried out in an inert gas atmosphere at a temperature of from 180 to 230 ° C, which results in a product with an average characteristic viscosity of 0.75 to 0.85 dL / year The granulated solid phase polycondensation product, usually considered the final product, is sold. Its processors, first of all, are manufacturers of solid bodies, which have equipment for molding. Various types of molding equipment, such as injection molding machines or blow molding machines, are known to those skilled in the art. Often, machines made on the principle of injection molding, produce semi-finished products, so-called preformed blanks, from which at a different technological stage, implemented in other processing plants, located, as a rule, in a different place, using a blow molding method, polyester bottles are made. The method proposed in the present invention makes it possible to process polyester granules also by other molding methods, for example, on machines intended for the manufacture of sheet and film materials.

The need for a solid phase polycondensation stage is mainly due to two reasons. To obtain finished bottles with a sufficiently high stability of the mechanical properties, the viscosity of the original polyester should exceed the level of viscosity adopted for polyesters used in the textile industry. Furthermore, as it is possible to cause less damage to the taste the products stored in bottles made from polyethylene terephthalate, the acetaldehyde content in the effluent from the final reactor polymer melt comprising between 30 to 70 million ^-1, after the solid phase polycondensation should not exceed 1 million ^-1 .

Acetaldehyde is an inevitable by-product, usually formed during the synthesis of polyethylene terephthalate. The content of acetaldehyde in the finished bottles should be kept at a low level, first of all, so as not to cause damage to the taste qualities of the products packaged in them. The content of acetaldehyde in polyethylene terephthalate can be regulated to a certain extent by varying the conditions for the implementation of the polycondensation stage and the subsequent stage of solid-phase polycondensation. Depending on the pretreatment of the polymer melt (its “thermal history”), the conditions of solid phase polycondensation and the mode of operation of the preforming machine, acetaldehyde is again formed during the implementation of the melting stage of the granulate. In the process of making bottles on a blow molding machine, the concentration of acetaldehyde changes only very slightly.

The maximum allowable content of acetaldehyde in the finished bottles intended for the packaging of sugary drinks, 8 million is ^-1, and in bottles for packaging water 4 million ^-1.

The implementation of the solid-phase polycondensation process is associated with significant costs for the corresponding equipment, because, before proceeding with it, the initial amorphous polymer crumb should be crystallized at an appropriate labor-intensive stage to avoid sticking. The implementation of these two stages requires a significant consumption of inert gas, which after use is subject to additional purification, so that it can be returned to the process.

- 1,011,146

In connection with the recent significant growth in demand for polyester bottles, installations for the manufacture of preformed blanks have reached such large sizes that it seems economically feasible to use our own installation for the synthesis of polyesters solely to provide our own production of such blanks with raw materials. This would allow the finished polyester melt to be sent directly to the machines for the manufacture of preformed blanks.

Therefore, there have been repeated attempts to avoid the need for an extremely cost-intensive and time-consuming solid phase polycondensation stage, like direct production of fibers from a polycondensation melt.

Thus, for example, German patent No. 19503053 describes a method according to which a polymer melt leaving a polycondensation reactor is transferred to a pipeline zone with an inert gas and a non-volatile amide compound provided with mixing elements, and during vacuum degassing for the shortest possible period time and at the lowest possible shear load on the melt send it to the stage of manufacturing preformed blanks in the device for molding.

According to the German patent ΌΕ 19505680 to a polycondensation melt with a characteristic viscosity of from 0.5 to 0.75 dl / g, an inert gas is admixed, the melt is subjected to polycondensation in an evacuated reactor for additional condensation, ensuring the formation of a polymer with a characteristic viscosity of 0.75-0.95 dl / g, then immediately send it to the mold for injection molding.

European patent EP 0842210 proposes another possibility to avoid the solid phase polycondensation stage. In accordance with this publication, polycondensation in the melt is carried out until the characteristic viscosity is from 0.65 to 0.85 dl / g, the polyester is cooled, granulated and re-melted, after which it is freed from volatile substances such as acetaldehyde, forming a developed surface and rinsing with an appropriate rinse aid in an appropriate device.

European patent EP 0842211 proposes a method according to which a polycondensation melt is introduced into an extruder with suction of evolved gases and a compression zone of the polymer, simultaneously fed into it, and then the proper washing agent is removed and the melt treated in this way is sent directly to the molding device.

In European patent EP 0836548 described equipment for moving the polycondensation melt through the mixing section and distribution node in the device for injection molding without specifying other details of the implementation of the method.

U.S. Patent No. 6,099,778 describes a method in which a polycondensation melt is introduced directly into a molding device. Conditions for the implementation of the proposed method are the absence of cobalt used in the polycondensation of the catalyst, the addition of compounds that reduce the content of acetaldehyde, and degassing of the melt before it is fed into the device for molding, carried out under pressure of 25 mm Hg. Art. up to a practical normal pressure, and the device used for degassing can be, for example, an extruder with suction of evolved gases or other suitable conventional equipment. As the substances used to reduce the content of acetaldehyde, mainly polyamides, polyether amides and polyethylene isophthalate are indicated.

In the international application \ ¥ O 98/41381 described apparatus and a continuous method of manufacturing molded products from polyester with a low content of acetaldehyde from a polycondensation melt without intermediate solidification of the polyester. In this case, the polycondensation melt is mixed in an extruder under pressure with an inert gas, the melt is degassed under vacuum, and its interaction is carried out in a mixing zone with an acetaldehyde-lowering compound, after which it is immediately introduced into an injection molding device. As compounds that reduce the content of acetaldehyde, use, in principle, the same substances as those listed in the above US patent.

A similar process is described in European patent EP 0968243. A polycondensation melt is introduced into a mixing device, which can be a static mixer, a gear pump or an extruder. A means for preventing sticking of the polymer, for example nitrogen or carbon dioxide, and a means for reducing the content of acetaldehyde, for example polyamides or polyether amides, are fed into the mixing device. The melt from the mixing device through one or more nozzles is introduced into an intensive evaporator. In the evaporator, the melt is degassed under a vacuum of 5 to 50 mm Hg, and means can be added again to reduce the content of acetaldehyde.

The report of the company 1pusp1a-P | 5s11sg from 25./26.02.2003 reports about another process of manufacturing preformed blanks directly from a polycondensation melt. In accordance with it, a high-viscosity reactor designed for the production of polyethylene terephthalate prepolymer is built into the production line, in which the melt viscosity is increased to 0.85 dl / g. Then an agent is introduced into the melt to reduce the content of acetaldehyde and, if necessary, other

- 2,011,146 additives and the mixture through the mixer is sent to the machine for injection molding.

German patent no. 10045719 proposes a method according to which a part of a polycondensation melt leaving the final reactor is separated and means for reducing the content of acetaldehyde are added to this separate melt flow in a twin-screw extruder, such as amides derived from polycarboxylic acids and polyfunctional amines, as well as polyesters stabilizers , such as triethyl phosphate. In a similar extruder, the gaseous reaction products are removed through a fitting intended for degassing. Then a separate melt stream is again connected to the main stream. The advantage of the described method is that the design of an expensive extruder with suction of evolved gases should be designed to process only part of the flow of the polycondensation melt, which reduces the cost of this extruder. However, the fundamental need for degassing the melt is preserved in this case.

Other possible means for reducing the content of acetaldehyde, at the use of which the solid phase polycondensation stage becomes unnecessary, are compounds proposed in U.S. Patent I8,627,212, which contain at least two hydrogen-substituted heteroatoms and interact with acetaldehyde in the polyester to form organic compounds, containing at least two heteroatoms in a non-bridged 5 or 6 membered ring. One of the possible compounds of this group is anthranilamide. Such additives in the form of a suspension can, for example, irrigate the polyester granulate used in the form of a granulated polyester masterbatch, or such additives can be mixed into the melt formed upon melting of the granulate.

The disadvantage of the above methods is that they require the use of expensive carrier gas for the melt degassing and the presence of an additional degassing unit, which forces the use of larger, respectively, more expensive process equipment, as well as the fact that acetaldehyde recurs adding means to reduce its content and can not be prevented in every case.

The present invention was based on the task of providing a method of continuous direct manufacturing of hollow bodies from aromatic polyesters and their copolymers, simplified from the point of view of the process equipment used and requiring as little as possible the cost of additional chemicals, which at the same time would allow to satisfy especially high claims to quality characteristics polyesters intended for the manufacture of hollow bodies, especially containers for the packaging of food products, and especially bu beverage packaging, such as viscosity, color and acetaldehyde content, or even improve these characteristics.

Unexpectedly, it was found that this problem can be solved by the method of manufacturing molded products from highly condensed polyester melt, according to which the melt between the polycondensation reactor, respectively the polycondensation reactors and the molding devices never solidifies and there are no any between the final reactor and the molding device Degassing devices.

The advantage of the proposed method consists in the absence of the need to use an additional solid phase polycondensation stage with the necessary granulating device, gas crystallization and preparation unit and high gas costs, as well as in the design, manufacture and maintenance of an extruder with suction of released gases. The method similar to that proposed in the invention, according to the prior art is still unknown.

The process according to the invention is suitable for the manufacture of molded articles from highly viscous melts of aromatic polyesters or copolyesters, which can be synthesized from one or more dicarboxylic acids, such as terephthalic, isophthalic, naphthalene dicarboxylic and / or 4,4-bis-phenyldicarboxylic acid, respectively their methyl esters and one or more diols, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and / or diethylene glycol.

These starting compounds can be processed in a known manner into a highly viscous polyester melt by continuous methods of esterification or transesterification using known catalysts and subsequent melt polycondensation carried out under vacuum in modified polycondensation reactors. Polyethylene terephthalate is preferably used in the form of homopolymers or copolymers containing less than 10% by weight of comonomers.

The polymer melt from the final reactor through a specifically branched piping system is sent directly to the device for molding. The characteristic melt viscosity at the outlet of the final reactor is preferably from 0.74 to 0.85 dl / g. Since the performance of the final reactor in the event of a brief cessation of operation of one or more devices for molding, due to the need for their maintenance or malfunction, cannot be immediately adjusted to the changed number of the product selected by these devices, in a preferred embodiment of the method proposed in the invention up to 50 %, preferably up to 20% and particularly preferably at most 10% of the melt flow through the control valve return to the stage of esterification. Bypass this

- 3,011,146 parts of the melt are usually carried out after the pump used to discharge the melt from the final reactor. On the way to the esterification stage, the highly viscous melt is, if necessary, subjected to glycosidation by adding at most 10% ethylene glycol, after which the low-viscosity melt is returned to esterification.

Part of the main stream of the melt, if necessary, can be sent to the granulating device. The polyester granules obtained in this device may, for example, be processed by the manufacturer himself on a molding machine into preformed blanks or sold. Before processing the granulate obtained as above, into preformed blanks intended for the production of bottles, it is only necessary to carry out its modified drying, which prevents the insufficiently crystallized polymer chips from sticking together.

The melt portion bypass described above also allows the feed pressure of the molding devices to be adjusted independently of the actual performance of the final reactor. By bypassing part of the melt, first of all, balance the fluctuations in the selection of the melt in the molding machine.

Pressure control in the melt line is carried out directly in front of the molding devices and the pressure is set in the range from 1 to 20 bar, preferably 10 ± 1 bar by controlling the bypass of a part of the melt flow.

In accordance with the present invention, the primary flow is the melt flow in the path between the final reactor and the molding device. The main stream of the melt does not include flows that, after the bypass, are sent to the esterification and / or to the granulating device.

As a final reactor, for example, a polycondensation reactor designed for the synthesis of products with high characteristic viscosity can be used, for example, described in European Patent EP 0320586. The so-called two-drive reactor (manufactured by ΖίιιιηοΓ AC), described, is also particularly suitable as a final reactor for example, in US patent I8 3617225. Instead of a solid shaft, this reactor is equipped with a composite shaft, on which are mixing elements. Both halves of the composite shaft are driven in rotation by corresponding individual drives. This provides unlimited opportunities to bring the shaft rotational speed in accordance with the reaction conditions, first of all, the viscosity of the polymer melt.

To increase the technological flexibility of the installation, the intermediate product from the pre-condensation reactor can be sent to at least two parallel-connected final reactors, providing different molding devices with the starting material. This option is advisable to use, for example, if you want to synthesize products with significantly different final viscosity. In this case, both final reactors can be operated under different technological conditions and, nevertheless, the economic advantages of a plant with a large production capacity can be preserved to the maximum. The embodiments of the invention discussed below relate to the zone after the final reactor, regardless of whether one or more of the final reactors are fed from the precondensation reactor.

The melt exiting the final reactor is preferably directed to at least two molding devices. Before the first branching of the melt flow, depending on the pressure loss in the general system of its movement, in addition to the pump installed at the outlet of the final reactor, if necessary, provide an additional pressure-boosting device, which guarantees the continuity of the melt flow directed to the devices for forming.

The path to be overcome by the melt from the first pressure-boosting device to the molding devices should be calculated so that the design of the piping systems and the corresponding distances to the molding equipment are identical and, therefore, the entire melt is subjected to the same heat treatment as possible. This is achieved preferably due to the symmetric branching of the melt lines in accordance with the need. Within each section of the pipeline and before each branching by means of static mixing elements, it is preferable to re-align the temperature gradient established in the melt flow in the direction from its edge zones towards the middle. In this case, in the ideal case, the mixing elements should be located in front of the corresponding places of branching the flow as close as possible to them. The length of these static mixing elements does not exceed 1-6 times, preferably 1-3 times the value of the internal diameter of the pipeline.

To ensure optimal symmetry of the melt lines, the main stream of the melt leaving the final reactor should be directed to an even number of molding devices. Especially preferred is the ordering of the device for molding into sections consisting of four such devices. This means that the last branch divides the main stream into four pipelines, each of which leads directly to the corresponding molding device. To ensure symmetry, the previous branches divide the melt flow, respectively, into two pipelines. It follows that for each final reactor four, eight or sixteen, etc., molding devices are provided. Number of ramifications

- 4 011146 water depends on the overall performance of the installation and the individual performance of the devices used to form it. The number of consecutive branches is preferably between one and four.

To ensure the minimum content of acetaldehyde in the preformed blanks, a substance reducing the content of acetaldehyde or a mixture of substances reducing the content of acetaldehyde is added to the main melt flow before entering the molding device 1 or, maximum. In the future, such a substance, respectively, a mixture of such substances for simplicity is designated by the general term “additive”. The additive is evenly distributed in the polymer melt by means of static, if necessary cooled, mixing units built in the pipeline in alternating order, after which the additive interacts with the vinyl ether end groups of the molten polyester and / or the acetaldehyde present. The additive is introduced into the melt stream in the form of a solid, a mixture of solids or suspension, i.e. a suspension in a dispersing agent.

The additive may be a separate compound or a mixture of compounds that reduces the content of acetaldehyde in the polymer melt alone or in the aggregate. Such compounds are known from the prior art described in the literature.

The additive may also include compounds that, to the maximum extent, prevent the reaction of breakage of polyester chains and, therefore, reduce the initial formation of acetaldehyde. Such compounds are also known in the art. Phosphorus-containing substances are preferably used as such compounds. For example, it is possible to use carboxyphosphonic acid derivatives, in particular, those described in the German patent 19631068, the contents of which are incorporated into the present application by reference. Other phosphorus-containing stabilizers are given in German Patent No. 10337522. It was found that the simultaneous addition of representatives of both the above mentioned classes of substances contributed to a particularly significant decrease in the content of acetaldehyde in preformed blanks.

If the additive is introduced into the process as a suspension, then a compound that also participates in the polycondensation reaction, such as ethylene glycol, should be used as a dispersing agent in the case of forming polyethylene terephthalate blanks. Suspended additive may contain other necessary substances, such as dyes, UV absorbers, means for reducing the content of oxygen and carbon dioxide. The additive is introduced into the melt using known from the prior art devices for the introduction of additives in the polyester melt. Suitable devices are described, for example, in German patents ΌΕ 19841376, 19851948 and 10049617, however, other devices suitable for the addition of additives can also be used. In any case, for the successful application of the present invention, it is important to ensure the short duration of the polymer melt in the zone between the final reactor and the molding equipment, as well as uniform distribution of additives in the melt, and, in particular, the formation of dead zones should be avoided.

It is advisable to arrange the first device for the introduction of additives on the melt line after the pump, designed to unload the polycondensation product from the final reactor, before the first branch of the melt line.

By introducing the additive at this point the maximum content of acetaldehyde in the preform is reduced to 25 million ^-1, preferably up to 8 million ^-1 and particularly preferably less than 4 million ^-1. If necessary, the indicated concentrations of acetaldehyde can be achieved by additionally introducing the additive directly in front of the molding machines. Thus, one of the preferred embodiments of the invention provides an additional device for the introduction of additives, located after the last branching of the melt line before the corresponding device for molding. Therefore, the additive can be introduced in two consecutive places on the main flow line. Due to this, the metered amounts of the additive can be adjusted to the need, for example, they can be matched with the amount of acetaldehyde re-formed during the transfer of the melt. By means of a second metering device, it is possible to additionally introduce dyes, UV stabilizers, additives that improve barrier properties or increase thermal stability, and similar substances. Mixing and uniform distribution of these substances in the melt is carried out both by means of static mixing elements and in the mixing zone of the molding machine. The system described above allows to produce, for example, preformed bottle blanks that satisfy the most varied requirements.

In another preferred embodiment of the process according to the invention, an additive is introduced by means of a first device for introducing additives, which may contain both a stabilizer and an acetaldehyde-reducing substance. The addition of a stabilizer allows you to limit the possible staining of the polyester, due to the use of nitrogen-containing substances to reduce the content of acetaldehyde. It is especially preferred to use a stabilizer selected from the group of carboxyphosphonic acids.

For effective control of acetaldehyde content in molded products, stay

- 5 011146 of the melt in the area between the place of the last injection of the additive and the entrance to the molding device should be as short as possible. Preferred is such a design of the specified zone, according to which the average residence time of the melt in it does not exceed 6 minutes, preferably 2 minutes.

The amount of additives to be dispensed depends on the content of acetaldehyde in the main stream of polymer melt leaving the final reactor, its residence time in the melt line, its temperature and the desired final concentration of acetaldehyde in the molded product. The longer the residence of the molten polymer in the melt line, the more additives must be added.

The average residence time of the polymer melt in the zone between the final reactor and the entrance to the device for molding cannot be arbitrary. However, it inevitably increases with increasing production capacity of the final reactor, since in this case the melt is distributed into a larger number of molding devices, which requires the use of a larger number of branching steps, as well as a combination of longer melt lines.

In any case, it is preferable that the maximum average residence time of the melt in the zone between the final reactor and the entrance to the molding apparatus is 30 minutes, preferably 15 minutes, particularly preferably 12 minutes.

In order to avoid the formation of a temperature gradient and intense local degradation of the polymer melt, static mixers with alternating arrangement are used, which counteract the anticyclic mixing of the edge zones of the melt flow with its core.

To ensure that the melt stays as short as possible in the zone between the final reactor and the entrance to the molding device, the static mixers should be as short as possible. The length of the static mixers preferably does not exceed six times, especially preferably three times the internal diameter () of the section of the pipeline within which they are installed.

Machines currently used to manufacture preformed blanks have a design suitable for frequent, for example, moving that part of the machine into which the melt goes, at least once a day, from the working position to the maintenance position for cleaning and maintenance. . Such maintenance is not associated with any problems if polymer granules are fed into the machine as the starting material and it is equipped with an extruder designed for its melting. However, according to the method of the present invention, a highly viscous polymer melt is sent to a molding device through a rigidly mounted pipeline provided with a double jacket.

According to the invention, in order to properly connect the last device for introducing additives with the movable machine, a flexible pipe is used, for example, a scissor swivel joint as a permanent connection of a rigidly fixed pipeline with the movable machine. Scissor swivel allows you to compensate for the maximum horizontal movement of the forming machine 100 cm, preferably 50 cm and particularly preferably 30 cm. At the same time, the hinges can be horizontal with vertical axes of rotation or vertical with horizontal axes of rotation.

In the transition zone to the machine for the manufacture of preformed blanks should ensure a constant pressure of the polymer melt. In order to guarantee a constant supply of melt to the molding machine, its pressure must be set in the range from 1 to 20 bar and preferably it is 10 ± 1 bar. According to the invention, the pressure of the melt is controlled by by-passing a variable amount of excess melt into the esterification stage and / or into the granulating device. The pressure of the melt is measured directly in front of the machine for the manufacture of preformed blanks. The preferred temperature of the melt is from 280 to 285 ° C.

The diagram shows an example of the implementation proposed in the invention method and the proposed invention in the device, not limiting the scope of the invention.

High viscosity prepolymer having the required viscosity, obtained in the final reactor 1 intended for precondensation, for example, in a high viscosity self-cleaning or double-drive reactor, is discharged from it using a discharge pump 2. After passing through a threefold static mixing element with a length of 3 X 3Ό into the melt flow through the first device for the introduction of additives enter the required amount of the additive and, if necessary, other substances and evenly distribute them into p alloy means adjacent to an apparatus for introducing additives static mixer element length 15Ό. To compensate for pressure losses in the system of branches to machines for the manufacture of preformed blanks, it is possible to use a booster pump 5 pressure boosting. The feed pressure in front of the machines is controlled by measuring it with a sensitive element of a RS type pressure sensor and bypassing part of the main melt flow into the granulator 7 by means of a regulating bypass pump 6. Similarly, a part can be returned bypass

- 6 011146 th melt by means of the second, not shown in the scheme, bypass pump to the also not shown esterification stage. The main stream of the melt through several branches goes to the machines for the manufacture of preformed blanks, with a static mixer 8 placed before each branch. After the last fork, the additive is again metered into the polymer melt by means of the second device and, if necessary, other substances are homogenized and the melt is additionally homogenized attached static mixer 8 and through a scissor swivel pipe not shown in the diagram is sent to the machine d I preforming.

Examples

Below the invention is described in more detail in some examples, in no way limiting its scope. The figures given in the examples were determined as follows.

Characteristic viscosity was determined at 25 ° C, using a solution of 500 mg of polyester in 100 ml of a mixture of phenol with 1,2-dichlorobenzene (mass ratio of 3: 2).

The concentration of terminal carboxyl groups was determined by photometric titration of a solution of polyester in a mixture of o-cresol with chloroform (mass ratio 70:30) with a 0.05 molar solution of caustic potash in ethanol with bromthymol blue as an indicator.

The coordinates of the colors b and b were determined by Hunter. First, the polyester crumb was subjected to crystallization, carried out for 1 h in an oven at 135 ± 5 ° С. Then, the color coordinates were determined in a three-band colorimeter by measuring the color tone of the polyester sample (X-, Υ- and Ζ-parameters) by three photocells with upstream filters (red, green and blue). The color coordinates were calculated by the formula of Hunter

Ε = 10 ^ Υ and

B = 7.0 ^ Υ (Υ-0.8467Ζ)

Acetaldehyde was desorbed from polyester by heating the sample in a closed vessel and analyzing the gas phase by chromatography using the H540 Regxix E1TeG injection system (nitrogen gas carrier; special steel column 1.5 m long; fixed phase Rogorask ^, 80-100 mesh; sample weight 2 g; heating temperature 150 ° C; heating time 90 min).

A sample of the product was taken and at an initial temperature of 35 ° C, it was heated at a rate of 10 K / min to 300 ° C, after which the melting point and the thermal energy necessary for melting were determined.

A high-viscosity melt of polyethylene terephthalate, designed for carrying out the experiments described in the examples, was obtained in a continuous-action reactor of the NU8R type (high-viscosity self-cleaning reactor) described, for example, in European patent application EP 0320586. The reactor is equipped with an internal shaft with heated blades of special shape and built-in blades with special shapes and embedded fittings in the process of highly viscous melt sticking to the shaft and the surface of the walls. The quality of the original product used commercial granules with a characteristic viscosity of 0.62 DL / g, intended for the manufacture of bottles for fruit juices, saturated with carbon dioxide. The granulate was dried, melted in a Nikktapp single-screw extruder and the melt was continuously fed into a highly viscous self-cleaning reactor, in which under mild conditions (pressure 0.1-0.5 mbar, temperature 275-280 ° C) were subjected to condensation with a capacity of 20 kg / h, to give the product a viscosity of 0,80-0,84 dl / g, acetaldehyde content of about 30 million ¹ and the color coordinate b between -3 and -4. The resulting product was continuously supplied with a gear pump through a pipeline equipped with static mixing elements of type 8МХ of the company 8 and 1хг. directly to a modified XB 160 machine for the manufacture of preformed blanks with a modified mixing zone equipped with a two-cavity working body and the possibility of simultaneous production of two preformed blanks, where the polymer was processed into appropriate blanks.

To meet different requirements, the number of mixing elements used in the experiments was varied, and the length of one mixing element always corresponded to the diameter of the pipeline (that is, it was 1Ό). Aligned triple mixing elements 3 X 3Ό in length were used to equalize the temperature gradient between the marginal and middle zones of the polymer melt along the pipeline, and for uniform distribution of the additive in the pipeline after the first device, 15Ό length mixing elements were used. During the second supply of the additive to the melt pipe directly in front of the movable scissor swivel with horizontal joints and vertical axes of rotation, only one additional mixing of additives was carried out by means of mixing elements with a length of 3Ό. The static distribution of additives was achieved only in the modified mixing zone of the machine for the manufacture of preformed blanks.

During the experiments, the amount of melt supplied to the machine for the manufacture of preformed blanks was varied in the range from 90 to 72% of the amount of melt coming from the final reactor by matching the melt feed with the machine operating mode.

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In this case, the setting of the supply of melt to the machine for the manufacture of preformed blanks was carried out by regulating its pressure in front of the machine. Pressure control was carried out by adjusting the bypass of the main stream of the melt after the first device for the introduction of additives using a gear pump. The overflow part of the melt was processed in a granulator into polymer chips. The resulting chips were dried in the crystallizer using nitrogen as the carrier gas, followed by crystallization and processing into preformed blanks.

To determine the product quality, laboratory control of the most important quality characteristics of the granulate and preformed blanks (ground under nitrogen atmosphere) using the methods described above was carried out.

Used additives, stabilizers and dyes were dosed through a Nazztapp side-flow extruder in combination with gear pumps. During the experiments, commercially available supplements were tested, both in liquid and solid states.

The most important technological parameters and quality indicators are shown in the following table. 1 and 2. At the same time, расп means the melt line diameter, b is the length of the melt line, b / o is the ratio of the length of the melt line to its diameter, 1 ₁ is the time the melt is in line to the second additive device, 1 ₂ is the time the melt in the area between the second device for the introduction of additives and the entrance to the machine for the manufacture of preformed blanks, p is the working pressure at the end of the melt line and T is the temperature of the melt after scissors hinge joints of pipes. Under the first introduction of additives, respectively, the second introduction of additives refers to the amount of additives and other substances dosed by the first, respectively, the second device for the introduction of additives. At the same time AA means a means for reducing the content of acetaldehyde of the firm Sosa-Co1a®, P - the stabilizer H-ΜΟΌ of the company Ρΐιάία and Ό - the dye Εδΐοίϊΐ V1ie of the company S1apap1.

Polyester melt outlet vysokovyazkostnogo self-cleaning reactor had the following characteristics: inherent viscosity 0.83 dl / g, content of carboxyl groups of 22 mmol / kg, an acetaldehyde content of 32 million ^-1 -3 color coordinate L units.

Table 1

Experience Units one 2 3 four five 6 7 Overall performance kg / h 20 20 20 20 20 20 20 Productivity of the forming car kg / h % 18 90 18 90 18 90 18 90 18 90 18 90 18 90 ϋ mm 20 20 20 20 20 20 20 one_ m five five five five ten ten ten and about 250 250 250 250 500 500 500 Ιι min 5.5 5.5 5.5 5.5 eleven eleven eleven with 285 285 285 285 285 285 285 R bar 20 20 20 20 20 20 20 t ⁶ С 282 282 282 282 284 284 284 The first introduction of additives million ^one Not 1000 AA 1000 AA 1000 AA 15P 1000 AA 15 Р 1000 AA 15 Р Not

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Second introduction of additives million ^one Not Not 500 AA 500 AA 500 AA 500 AA 0.5 β Not Preformed billet: Intrinsic viscosity dl / g 0.80 0.79 0.785 0.795 0.785 0.78 0.79 Cun mmol / kg 32 33 35 33 34 39 37 Acetaldehyde content million ^one 53 e, 5 2.5 2.0 3.0 6.0 64 Color coefficient b units 0.8 2.5 3.0 0 0.5 0.2 5.5

table 2

Experience Units eight 9 ten eleven 12 13 Overall performance kg / h 20 20 20 20 20 20 Produced by kg / h 18 14.4 18 18 18 18 Die Casting Machine % 90 72 90 90 90 90 0 mm 20 20 25 25 25 25 s m five five five ten 15 15 and about 250 250 200 400 600 600 Ιι min 5.5 5.5 8.6 17.2 26 26

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with 285 350 285 285 285 285 R bar 20 20 20 20 20 20 T ⁰ С 282 282 283 284.5 286 286 The first introduction of additives million ^one 1000 AA 15 Р 1000 AA 15P Not Not Not 1500 AA 25 Р Second introduction of additives million ^one 500 AA 500 AA Not Not Not 500 AA Preformed billet: Intrinsic viscosity dl / g 0.793 0.796 0.80 0.78 0.775 0.76 Cun mmol / kg 34 33 34 40 45 46 Acetaldehyde content million ^one 1.9 2.8 61 80 95 8.5 Color coefficient b units 0.3 0.9 1,3 5.7 5.9 3.4

From the results of experiments 1–7, the apparent effect of varying the residence time of the polymer on its destruction is evident, which is manifested in a decrease in the intrinsic viscosity and content of terminal carboxyl groups and an increase in the color coefficient L of preformed blanks. An additional destructive effect was also exerted by the use of means for reducing the content of acetaldehyde, however, this effect was almost completely compensated by the additional introduction of a stabilizing compound by means of the first device for the introduction of additives. The acetaldehyde content in the preform was reduced to an acceptable concentration for market distribution, i.e. less than 8 million ^-1. Improving the color contributed to the use of blue dye in a very small concentration of 0.5 million ^-1 .

In experiments 8 and 9, it was established that an increase in the residence time of the polymer melt in the zone between the second device for introducing additives and the entrance to the machine for the manufacture of preformed blanks, despite sharing the means for reducing the content of acetaldehyde and stabilizing compound in the first step of the introduction of additives, to a slight deterioration in the quality of the molded blanks.

In experiments 10-12, the effect of a further increase in the residence time due to an increase in the conditional passage of the polymer melt pipelines and the simultaneous increase in the melt temperature was investigated. This led to a further deterioration in the quality of the molded blanks, accompanied by an increase in the base content of acetaldehyde (that is, the content of acetaldehyde without the use of a reducing agent). To compensate the deterioration in experiment 13 increased the amount of agent for reducing the acetaldehyde content introduced by the first device for introducing additives at 150% and the concentration of stabilizer 10 million ^-1 (based on phosphorus). However, these measures did not completely eliminate the deterioration of the main quality indicators of the polymer. The acetaldehyde content in the preform was reduced to 8.5 million ^-1.

All the preforms that were preformed in tests 2-6, 8-9, and 13 were processed without any problems on a laboratory blow molding machine using a ZGOE EBO 01 mold and standard settings into 0.5 L embossed bottles. . The quality of the bottles met the requirements of the market.

The granulate obtained in the experiments crystallized and the contents contained in it were additionally removed.

- 10 011146 acetaldehyde by treating for 30 minutes at a temperature of 190 to 205 ° C in a U1Bga fluidized bed mold using nitrogen as a carrier gas, after which the granulate was dried for 4 hours at 170 ° C in a standard laboratory dryer before losing stickiness and subjected to processing in a laboratory machine for the manufacture of preformed blanks with a bilaterial mold company Nizku, getting preformed blanks weighing 28 g with an acetaldehyde content of 5-6 million ^-1 .

Claims (32)

1. A process for producing moldings with a maximum content of acetaldehyde in the preform 8 million ^-1 of highly condensed polyester melt, wherein as the final polycondensation reactor using a reactor of self-cleaning type reactor vysokovyazkostnogo or a dual-type reactor with a solid shaft or compound, the polymer melt is passed from the final reactor through a system of pipelines for its distribution directly to the molding device and to the flow before entering the molding apparatus 1 or at most 2 times, a substance that reduces the acetaldehyde content or a mixture of substances that reduce the acetaldehyde content is added before entering the molding apparatus. 2. The method according to claim 1, characterized in that from 50 to 100% of the melt emerging from the final reactor is fed to molding devices. 3. The method according to one of claims 1 to 2, characterized in that the supply pressure of the molding devices is controlled by bypassing part of the melt. 4. The method according to one of claims 1 to 3, characterized in that the pressure control in the melt line is carried out directly in front of the molding devices and set it in the range from 1 to 20 bar, preferably 10 ± 1 bar by regulating the melt overflow. 5. The method according to one of claims 1 to 4, characterized in that the by-pass part of the melt is returned to the esterification stage and, if necessary, also to a granulating device. 6. The method according to one of claims 1 to 5, characterized in that from 0 to 50% of the melt leaving the final reactor is returned to the esterification stage and to the granulating device. 7. The method according to one of claims 1 to 6, characterized in that a maximum of 20%, preferably a maximum of 10% of the melt leaving the final reactor is returned to the esterification step. 8. The method according to one of claims 1 to 7, characterized in that a maximum of 10% ethylene glycol is introduced into the highly viscous melt returned to the esterification stage. 9. The method according to one of claims 1 to 8, characterized in that at least two parallel end reactors are used, equipped with different molding devices. 10. The method according to one of claims 1 to 9, characterized in that the melt from the final reactor is directed to at least two molding devices. 11. The method according to one of claims 1 to 10, characterized in that at least one pressure-boosting pump is used before the first branching of the melt line. 12. The method according to one of claims 1 to 11, characterized in that the main stream of the melt is directed to an even number of molding devices. 13. The method according to one of claims 1 to 12, characterized in that a substance or mixture of substances in the solid state or in the form of a suspension is added to the melt stream before entering the molding device. 14. The method according to one of claims 1 to 13, characterized in that after the first pressure-boosting pump there is a device for introducing additives. 15. The method according to one of claims 1 to 14, characterized in that after the last branching of the melt line before each device for molding in the melt line is a device for introducing additives. 16. The method according to one of claims 1 to 15, characterized in that by means of devices for introducing additives located after the last branching of the melt line in front of different machines for manufacturing preformed blanks, different additives and / or various other substances are added to the melt. 17. The method according to one of claims 1 to 16, characterized in that the maximum average residence time of the melt between the last device for introducing additives and the entrance to the device for molding is 6 minutes, preferably 2 minutes 18. The method according to one of claims 1 to 17, characterized in that in the melt line after the first device for introducing additives, a static mixing element with a minimum length of 15 Ό is used, where Ό is the inner diameter of the pipeline section. 19. The method according to one of claims 1 to 18, characterized in that a static mixing element of a minimum length is used in the melt line after the second device for introducing additives immediately before the movable scissor articulation of the pipes, in which there are horizontally located hinges with vertical axes of rotation 3Ό. 20. The method according to one of claims 1 to 19, characterized in that the additive contains at least one - 11 011146 phosphorus-containing compound. 21. The method according to one of claims 1 to 20, characterized in that the additive contains at least one substance that reduces the content of acetaldehyde. 22. The method according to one of claims 1 to 21, characterized in that the maximum average residence time of the melt between the final reactor and the entrance to the molding device is 30 minutes, preferably 15 minutes and particularly preferably 12 minutes 23. The method according to one of claims 1 to 22, characterized in that the melt line between the last device for introducing additives and the entrance to the molding device allows the molding device to move horizontally at least 100 cm, preferably at least 50 cm , particularly preferably max. 30 cm. 24. The method according to one of claims 1 to 23, characterized in that the melt line is designed for a maximum working pressure of 200 bar and a maximum temperature of 320 ° C, preferably 280-285 ° C. 25. A method of manufacturing molded articles from a highly condensed polyester melt, according to which from 50 to 100% of the type of high viscosity self-cleaning reactor or type of two-drive reactor leaving the final reactor are sent to molding devices, the bypassed part of the melt is returned to the esterification stage and, if necessary, also to the granulating device, the polymer melt flow is directly directed to an even number of molding devices, after the last branch melt line in front of each molding device in the melt line there is a device for introducing additives, at least one substance that reduces the content of acetaldehyde, or at least one mixture of substances that reduce the content of acetaldehyde, is added to the polymer melt stream before entering the molding device solid state or in the form of a dispersion, and the polymer melt is passed from the final reactor through a piping system to distribute it directly to the molding device, azom, the melt between the polycondensation reactor, polycondensation reactors, respectively, and devices for forming never solidifies and between end reactor and molding device lacks any apparatus for degassing. 26. A device for the manufacture of molded products from a highly condensed polyester melt, characterized in that the final polycondensation reactor, such as a high viscosity self-cleaning reactor or a two-drive reactor type, is directly connected through the piping system to the molding devices and on the melt line between the polycondensation reactor and the molding devices no more than two devices for the introduction of additives. 27. The device according to p. 26, characterized in that the parallel pipelines for supplying a stream of polymer melt to the molding machines have the same design. 28. The device according to one of paragraphs.26-27, characterized in that to ensure uniformity of the melt using static mixers with a maximum length corresponding to one to six times, preferably one to three times the value of the inner diameter of the pipeline, installed in alternating order, but at least least before each branching of pipelines. 29. The device according to one of paragraphs.26-28, characterized in that the pipeline between the last device for introducing additives and the molding machine is so flexible that it allows the horizontal movement of the molding machine. 30. The device according to one of paragraphs.26-29, characterized in that for the permanent connection of the rigidly fixed line of the melt with the molding machine using a flexible pipe containing a scissor joint, the hinges of which have only vertical or only horizontal axis of rotation. 31. The device according to one of paragraphs.26-30, characterized in that the melt line between the last device for introducing additives and the molding machine allows the maximum horizontal movement of the machine per 100 cm, preferably 50 cm, particularly preferably 30 cm 32. The device according to p. 26, characterized in that between the last device for introducing additives and the molding machine, it contains a pipeline that allows horizontal movement of the molding machine.